Showing papers in "Journal of Environmental Engineering in 2000"
TL;DR: In this article, the anaerobic hydrolysis rate of organic solid waste was studied at fixed volatile fatty acid (VFA) concentrations ranging from 3 to 30 g COD/L and fixed pH values between 5 and 7.
Abstract: The anaerobic hydrolysis rate of organic solid waste was studied at fixed volatile fatty acid (VFA) concentrations ranging from 3 to 30 g COD/L and fixed pH values between 5 and 7. For separate control of both VFA and pH, a special completely mixed reactor was designed. In this way, it was possible to distinguish between the inhibitory effects of pH, total VFA, and undissociated VFA on anaerobic hydrolysis. It was shown that hydrolysis of the organic solid waste followed first-order kinetics. Using a statistical analysis, it was found that the hydrolysis rate constant was pH dependent but was not related to the total VFA and undissociated VFA concentrations.
287 citations
TL;DR: In this article, a combined electrocoagulation and electroflotation process was applied to restaurant wastewater treatment, where the effects of operational variables on performance were examined, and the results showed that the combined process showed promising performance.
Abstract: A combined electrocoagulation and electroflotation process was applied to restaurant wastewater treatment. The effects of operational variables on performance were examined. The electrocoagulation ...
269 citations
TL;DR: In this article, the removal of As(III), As(V), Hg(II), and Pb(II) by virgin and Fe(III) impregnated activated carbons (FeAC) was investigated.
Abstract: The removal of As(III), As(V), Hg(II), and Pb(II) by virgin and Fe(III) impregnated activated carbons (FeAC) was investigated. Iron-oxide impregnation increased the pHzpc of the carbon from 7.5 to about 8.2–8.7 but did not alter the surface area or the pore volume. The amount of acid or base needed to reach a given pH increased following impregnation, indicating that the FeAC was more active than its non-impregnated counterpart. Metal removal was a function of pH with removal increasing with pH for Hg(II) and Pb(II) and decreasing with pH for As(V). As(III) removal was not a strong function of pH below pH = 5, increased to a maximum at pH ≈ 7, then decreased with increasing pH. As(III) and As(V) removals were about one and two orders of magnitude higher, respectively, for the FeAC compared with the non-impregnated carbon, while Hg(II) and Pb(II) removals were only slightly higher. Fe-impregnation appears to be most effective for the anionic contaminants.
198 citations
TL;DR: In this article, the results of research into the pollutants in runoff from road pavement surfaces following natural rainfall events were examined at 21 sites centering around Brisbane, in southeast Queensland, Australia.
Abstract: This paper examines the results of research into the pollutants in runoff from road pavement surfaces following natural rainfall events. Road runoff water quality was monitored at 21 sites centering around Brisbane, in southeast Queensland, Australia. The sites were selected according to traffic volumes, surrounding land use, pavement surface type, ease of access, and commercial vehicle percentage. Bridge sites were chosen for convenience of sample collection and minimized infrastructure modification. "First flush" grab samplers were permanently installed at each site to collect the first 20 l of runoff from one of the bridge drainage scuppers. The runoff samples were tested for a number of heavy metals, hydrocarbons, pesticides, and other physical characteristics. The observed results fall within the ranges of concentrations reported internationally and nationally but do not typically follow the 30,000 average annual daily traffic results reported in the United States. Traffic volumes have not been found to be the best indicator of road runoff pollutant concentrations. Interevent duration has been found to be a significant factor for pollutant concentrations. Sites incorporating exit lanes have recorded higher concentrations of acid-extractable copper and zinc, tending to support the hypothesis that brake pad and tire wear caused by rapid deceleration contributes to the concentrations of these metals in road runoff. Laser particle sizing has shown that a significant proportion of the sediment found in the runoff is smaller than 100 micrometers. However, these particulates do settle in water within 24 hours, under laboratory conditions. This may be due to the presence of heavy metals.
191 citations
TL;DR: In this article, a mathematical formulation is developed that avoids these problems of ambiguity and eclipsing, and the recommended index form is open to increasing the number of variables included within the index.
Abstract: Alternative efforts to describe water quality by an aggregate index consisting of subindices of the constituent quality variables are examined. Ambiguity problems exist where all the subindices are acceptable and yet the overall index is not. Eclipsing problems exist where the overall index is insensitive to a single variable; such insensitivity is unacceptable. A mathematical formulation is developed that avoids these problems of ambiguity and eclipsing. Furthermore, the recommended index form is open to increasing the number of variables included within the index.
168 citations
TL;DR: In this article, the competition of copper, lead, and cadmium adsorption on goethite was studied and found to be dependent on metal ion and oxide surface characteristics.
Abstract: Competition of copper, lead, and cadmium adsorption on goethite was studied and found to be dependent on metal ion and oxide surface characteristics. In adsorption edges, ionic strength effects suggested copper, lead, and cadmium are specifically adsorbed on goethite. Metal capacity on the goethite surface was found to increase with metal electronegativity: Cu > Pb > Cd. On the other hand, the equilibrium constant for lead was greater than that of copper, which is in agreement with their hydrated radii (Pb < Cu < Cd). Modeling revealed that the single-site Langmuir isotherm described the Cu-Cd and Pb-Cd adsorption and competition results within the error of the model. Furthermore, although the model provided a good fit for Pb and Cd data in the Pb-Cu and Pb-Cu-Cd systems, it underpredicted copper adsorption. The difference in site densities between copper and lead revealed a set of sites not available for competition. Using this approach where copper affinity is equivalent for both sites, the model provid...
140 citations
Journal Article•
TL;DR: In this article, a large data set of reaeration-rate coefficient (iK-d2) measurements made with tracer-gas methods was compiled from U.S. Geological Survey studies.
Abstract: Accurate estimation of the reaeration-rate coefficient (\\iK\\d2) is extremely important for waste-load allocation. Currently, available \\iK\\d2 estimation equations generally yield poor estimates when applied to stream conditions different from those for which the equations were derived because they were derived from small databases composed of potentially highly inaccurate measurements. A large data set of \\iK\\d2 measurements made with tracer-gas methods was compiled from U.S. Geological Survey studies. This compilation included 493 reaches on 166 streams in 23 states. Careful screening to detect and eliminate erroneous measurements reduced the data set to 375 measurements. These measurements were divided into four subgroups on the basis of flow regime (channel control or pool and riffle) and stream scale (discharge greater than or less than 0.556 m³/s). Multiple linear regression in logarithms was applied to relate \\iK\\d2 to 12 stream hydraulic and water-quality characteristics. The resulting best-estimation equations had the form of semiempirical equations that included the rate of energy dissipation and discharge or depth and width as variables. For equation verification, a data set of \\iK\\d2 measurements made with tracer-gas procedures made by other agencies was compiled from the literature. This compilation included 127 reaches on at least 24 streams in at least seven states. The standard error of estimate obtained when applying the developed equations to the U.S. Geological Survey data set ranged from 44 to 61%, whereas the standard error of estimate was 78% when applied to the verification data set.
126 citations
TL;DR: In this article, total petroleum hydrocarbon degradation was monitored in a field site with three vegetative treatment plots, and one control plot undergoing natural attenuation within each treatment, TPH concentrations were monitored at 20 locations over time to study the phytoremediation potential of different vegetative treatments.
Abstract: Laboratory studies have shown phytoremediation to be a feasible method for remediating surface soils contaminated with organic compounds. Evaluation of this technology in the field is difficult because of the inherent spatial heterogeneity in the hydraulic and chemical properties of the soil. In this study, total petroleum hydrocarbon (TPH) degradation was monitored in a field site with three vegetative treatment plots, and one control plot undergoing natural attenuation. Within each treatment, TPH concentrations were monitored at 20 locations over time to study the phytoremediation potential of the different vegetative treatments. For comparing the performance of these treatments in a quantitative manner, first-order kinetics were assumed to be applicable at the local scale. The degradation rates and the initial contaminant concentrations were treated as spatially correlated random fields. Field-scale behavior was evaluated based on temporal variations of the means and variances of concentrations. Our results indicate the importance of spatial variability for an accurate assessment of phytoremediation in the field. From the degradation rate constants and mean reduction in TPH, rye grass and St. Augustine grass appear to be superior to sorghum and the unvegetated control in reducing contaminant concentrations in the field.
116 citations
TL;DR: An immobilized-cell membrane bioreactor was fabricated to investigate degradation of phenol at high concentrations using Pseudomonas putida American Type Culture Collection 49451 and it was observed that cells diffused from the membranes when phenol concentrations reached noninhibitory levels in a few experiments.
Abstract: An immobilized-cell membrane bioreactor was fabricated to investigate degradation of phenol at high concentrations using Pseudomonas putida American Type Culture Collection 49451. In the case of suspension cultures, P. putida utilized phenol at concentrations below 1,000 mg/L, but experienced substrate inhibition at higher concentrations. On the other hand, cells immobilized in 25% by weight polysulfone fibers degraded phenol at concentrations above 1,000 mg/L. At an initial phenol concentration of 1,200 mg/L, phenol was fully degraded within 95 h in the immobilized system, whereas no cell growth and phenol degradation were observed in the free suspension system at 1,000 mg/L phenol. In the immobilized system, it was observed that cells diffused from the membranes when phenol concentrations reached noninhibitory levels in a few experiments. In such cases, the time taken for complete degradation was shorter with cell diffusion because suspension cells were responsible for the rapid phenol degradation. Furt...
114 citations
TL;DR: In this article, the authors investigated the advanced oxidation of commonly used reactive dyestuffs in exhausted dye-bath effluents in homogeneous (H2O2/UV-C and photo-Fenton) and heterogeneous (TiO2-UV-A) media, and compared the treatment efficiencies of two different TiO2 powders (PC 500 and Mikroanatas) and the platinized Degussa P25 in varying pH media.
Abstract: This study investigated the advanced oxidation of commonly used reactive dyestuffs in exhausted dye-bath effluents in homogeneous (H2O2/UV-C and photo-Fenton) and heterogeneous (TiO2/UV-A) media. Photocatalytic treatment efficiencies of two different TiO2 powders (PC 500 and Mikroanatas) and the platinized Degussa P25 were compared with that of the more well-known Degussa P25 in varying pH media. Treatment performance was strongly affected by the initial H2O2 concentration for H2O2/UV-C and photo-Fenton oxidation systems, whereas for the TiO2/UV-A process only PC 500 TiO2 powder, an anatase crystal phase of the semiconductor, exhibited a significantly pH-dependent reaction efficiency. The decolorization rate followed the order of Fenton/UV-C > Pt-P25/UV-A > Mikroanatas/UV-A > P25/UV-A > PC 500/UV-A > H2O2/UV-C, whereas the decreasing order for total organic carbon reduction was Fenton/UV-C > H2O2/UV-C > Mikroanatas/UV-A > Pt-P25/UV-A > P25/UV-A > PC 500/UV-A for the studied reaction conditions. Removal of...
112 citations
TL;DR: In this paper, two wet detention ponds were investigated for their ability to remove pollutants, primarily phosphorus, from storm water runoff in the Phantom Lake watershed, a subbasin of the Lake Sammamish watershed in Bellevue, Washington.
Abstract: Two wet detention ponds were investigated for their ability to remove pollutants, primarily phosphorus, from storm water runoff. The two ponds lie within the Phantom Lake watershed, a subbasin of the Lake Sammamish watershed in Bellevue, Wash., which is developed as a commercial and residential area with impervious surface area as high as 57%. There are design differences between the two ponds, yet both are comparable to design recommendations set forth by local agencies. One pond was built for flow attenuation and water quality treatment; the other serves only to improve water quality. Fifteen storms and two baseflows were successfully sampled during the Northwest's wet season from October 1996 through March 1997. Pollutant removals varied between one-fifth and one-half for phosphorus, and greater than one-half for total suspended solids and most of the analyzed metals. Removal efficiencies were consistently better in the pond designed primarily for water quality.
TL;DR: In this article, a pilot scale fluidized bed reactor (FBR) was used to control the precipitation of struvite from sludge lagoon supernatant using a seed media.
Abstract: Controlled precipitation of struvite from postdigestion, sludge lagoon supernatant was studied using a pilot scale fluidized bed reactor (FBR). The process effectively and rapidly removed struvite constituents from the supernatant and produced effluent significantly undersaturated for struvite. Recently published information on struvite thermodynamic and kinetic properties was incorporated into the FBR system design and selection of components. Struvite crystals were selected as seed media, which enabled precipitation of nearly pure crystals and allowed nucleation, with its associated lag time, to be bypassed. Mixing energy in the FBR was demonstrated to be sufficient to overcome transport limitations to struvite growth, allowing growth kinetics to be governed by the surface integration rate of constituent ions into the growing crystal lattice structure. Struvite removal was optimized by incorporating pH elevation into the FBR system. Process fluid was circulated in the pH adjustment tank/FBR system, which was configured as a continuous feed stirred-tank reactor. Struvite removal efficiency exceeded 80% in continuous feed experiments where the hydraulic detention time exceeded 1 h.
TL;DR: In this article, the effect of hydraulic retention time (HRT) on the acidogenesis of dairy wastewater was studied using an upflow reactor at pH 5.5, 37°C, and six HRTs ranging from 4 to 24 hours.
Abstract: Effect of hydraulic retention time (HRT) on the acidogenesis of dairy wastewater was studied using an upflow reactor at pH 5.5, 37°C, and six HRTs ranging from 4 to 24 h. Results showed that the degree of acidification increased rapidly with HRT from 28.2% at 4 h to 54.1% at 12 h; further increase of HRT to 16 and 24 h only increased acidification slightly to 55.8 and 59.1%, respectively. The biodegradability of the three major constituents in dairy wastewater increased with HRT, following the order of carbohydrates > proteins > lipids. The predominant products were acetate, propionate, butyrate, lactate, and ethanol.
TL;DR: The chemical composition, molecular weight distribution, and biodegradability of soluble microbial products (SMPs) in an anaerobic baffled reactor (ABR) treating low-strength wastewater were investigated in this paper.
Abstract: The chemical composition, molecular weight (MW) distribution, and biodegradability (both aerobic and anaerobic) of soluble microbial products (SMPs) in an anaerobic baffled reactor (ABR) treating low-strength wastewater were investigated. The effect of various process parameters on the production of SMPs was also examined. Results indicated that high MW (>300 kDa) compounds were produced in the middle compartments of the reactor and formed 22% of the effluent chemical oxygen demand (COD). This fraction was found to be 86% degradable under aerobic conditions but only 4% under anaerobic conditions. Low MW (<1 kDa) material represented the highest portion (36%) of the effluent COD and was mainly found in the first compartment of the ABR and in the effluent. This fraction was more easily degraded under anaerobic conditions (33%) than aerobic conditions (17%). Analysis of a hydrolyzed sample of the high MW fraction revealed the presence of several sugars and volatile fatty acids. Therefore, it was concluded that the high MW material contains heteropolysaccharides. Nuclear magnetic resonance analysis of the low MW fraction revealed the possible presence of alcohol, carboxylate, and aromatic chemical groups. SMP production increased with increasing hydraulic retention time (HRT), probably due to enhanced biomass decay at high HRTs, and also increased with decreasing temperature, probably due to increased stress on the biomass and a reduced metabolism of the SMP at low temperatures. Finally, SMP production in an ABR containing higher levels of initial biomass concentration was greater than for an ABR operating at the same conditions but with lower levels of initial biomass.
TL;DR: The biosurfactant enhanced the solubilized naphthalene to more than 30 times its aqueous solubility, and the results are compared to an anionic (sodium dedecyl sulfate) and a nonionic (Triton X-100) surfactant.
Abstract: Biosurfactant was produced by fermenting kerosene and used vegetable oil using a Pseudomonas sp. under nonsterile conditions. The biosurfactant at a concentration of 0.5 g/L and pH of 10.5 lowered the surface tension of water to 25 mN/m. The biosurfactant was used to enhance the solubility of naphthalene, and the results are compared to an anionic (sodium dedecyl sulfate) and a nonionic (Triton X-100) surfactant. The biosurfactant (5 g/L at pH of 7) enhanced the solubility of naphthalene to more than 30 times its aqueous solubility. Solubilized naphthalene in Triton X-100 and biosurfactant solutions was biodegraded by the same microorganism that produced the biosurfactant. Naphthalene solubilized in biosurfactant and Triton X-100 (400–600 mg/L) was biodegraded in 40 days and 100 h, respectively. Naphthalene in the amount of 30 mg/L was degraded by the Pseudomonas sp. in 2 days. The biosurfactant was also biodegraded during the biodegradation of naphthalene, but this was not the case with Triton X-100. The...
TL;DR: In this article, an industrial wastewater from a food dye manufacturer was fed to a second laboratory-scale anaerobic baffled reactor at a concentration of 5% (volume-to-volume ratio) and then increased to 10%.
Abstract: Synthetic organic colorants, the majority of which are recalcitrant in nature, are used universally in many different manufacturing processes. The dyes are released into the environment in industrial effluents and are highly visible even at low concentrations ( 20 g/L) to inhibitory (IC\D50\N = 0.2 mg/L). Batch biodegradability assays indicated that the dyes were not readily utilized by the anaerobic microorganisms as a sole substrate. Decolorization of the dye tartrazine was investigated in a laboratory-scale anaerobic baffled reactor at a concentration of 250 mg/L. Reduction in COD of 50–60% and color reduction of about 95% was achieved. Initially the tartrazine was not readily decolorized; however, decolorization improved with acclimation of the biomass. An industrial wastewater from a food dye manufacturer was fed to a second laboratory-scale anaerobic baffled reactor at a concentration of 5% (volume-to-volume ratio) and then increased to 10%. Anaerobic degradation of the wastewater was efficient. Methanogenic activity was high; the organic content of the influent was reduced by about 70%, and color was reduced by almost 90%.
TL;DR: A new theory for the molecular mechanism of sludge granulation, namely proton translocation-dehydration theory, was proposed in this study, based on the consideration of biological activity of the bacterial cells.
Abstract: A new theory for the molecular mechanism of sludge granulation, namely proton translocation-dehydration theory, was proposed in this study. Based on the consideration of biological activity of the bacterial cells, the bacterial surface dehydration caused by proton translocating activity was suggested to initiate the sludge granulation. The overall granulation process in this new theory included four stages: dehydration of bacterial surfaces, embryonic granule formation, granule maturation, and postmaturation. Some phenomena involved in practical sludge granulation were adequately explained by this new theory.
TL;DR: In this article, a numerical model to compute the free-surface flow hydrodynamics and stream temperature is presented by solving the depth-averaged, 1D unsteady flow and heat transport equations.
Abstract: A numerical model to compute the free-surface flow hydrodynamics and stream temperature dy- namics by solving the depth-averaged, 1D unsteady flow and heat transport equations is presented. The hydro- dynamics model considers the effects of arbitrary stream geometry, variable slopes, variable flow regimes, and unsteady boundary conditions. The thermal transport model accounts for the effects of solar radiation, air tem- perature, relative humidity, cloud cover, wind speed, heat conduction between water and streambed, subsurface flow, and shading by riparian vegetation. The model is verified with measurements in a stream in an upland agricultural watershed located in Indiana. Diurnal variations in the streamflow and stream temperatures are highly transient. The proposed model predicted well the streamflow and stream temperatures that were measured every 15 min over 25 days. The results of this study demonstrate that the solar (shortwave) radiation and subsurface inflow are the most significant contributors to the stream heat budget. model was successfully applied in a steep channel where tem- poral change in flow is not abrupt. The solution of the com- plete hydrodynamics equation is necessary to incorporate the inertial terms, variety of channel slopes, and abrupt boundary conditions in small streams. In this paper, fully hydrodynamic and heat transport models are developed and coupled for water temperature and stream- flow prediction in streams. The model considers air-water heat exchange, sediment-water heat exchange, lateral heat inflow/ outflow, subsurface inflow/outflow, and the interaction be- tween solar radiation and riparian vegetation. The proposed model is verified with measurements in Little Pine Creek, Tip- pecanoe County, Ind. Good agreement between field measure- ments and model prediction is reported.
TL;DR: In this article, the effect of H2O2 and Fe 21 dosages on the decomposition of 2-chlorophenol (2-cp) using a coupled ultrasound/Fe 21 /H 2O2 process was investigated.
Abstract: One of the toxic and refractory pollutants formed during the color removal of fertilizer, chemical, and petroleum industrial effluents by chlorine is 2-chlorophenol (2-cp). The objective of this study is to inves- tigate the effect of H2O2 and Fe 21 dosages on the decomposition of 2-cp using a coupled ultrasound/Fe 21 /H 2O2 process. The extent of 2-cp decomposition and mineralization depends on the dosages of H2O2 and Fe 21 . More than 99% of 2-cp was decomposed and 86% of 2-cp was mineralized using the ultrasound/Fe 21 /H 2O2 process at Fe 21 of 10 mg/L and H 2O2 of 500 mg/L. Oxidation-reduction potential (ORP) monitoring is a useful method for determining the decomposition efficiency of the target compound. There was a slight increase in the ORP values with increasing Fe 21 dosages, and an apparent increase with increasing H 2O2 dosages was observed. The major intermediate formed during the decomposition of 2-cp was 2-chloro-p-benzoquinone. It was also readily decomposed using the coupled ultrasound/Fe 21 /H 2O2 process.
TL;DR: A laboratory-scale upflow anaerobic sludge blanket (UASB) reactor was used in this study to produce granular sludge at mesophilic temperatures (35 1C) and after more than 150 days of operation, a COD was found to be stable.
Abstract: A laboratory-scale upflow anaerobic sludge blanket (UASB) reactor was used in this study to produce granular sludge at mesophilic temperatures (35 1C). After more than 150 days of operation, a COD ...
TL;DR: In this paper, a Bayesian uncertainty analysis approach is developed as a tool for assessing and reducing uncertainty in ground-water flow and chemical transport predictions, which is illustrated for a site contaminated with chlorinated hydrocarbons.
Abstract: A Bayesian uncertainty analysis approach is developed as a tool for assessing and reducing uncertainty in ground-water flow and chemical transport predictions. The method is illustrated for a site contaminated with chlorinated hydrocarbons. Uncertainty in source characterization, in chemical transport parameters, and in the assumed hydrogeologic structure was evaluated using engineering judgment and updated using observed field data. The updating approach using observed hydraulic head data was able to differentiate between reasonable and unreasonable hydraulic conductivity fields but could not differentiate between alternative conceptual models for the geological structure of the subsurface at the site. Updating using observed chemical concentration data reduced the uncertainty in most parameters and reduced uncertainty in alternative conceptual models describing the geological structure at the site, source locations, and the chemicals released at these sources. Thirty-year transport projections for no-action and source containment scenarios demonstrate a typical application of the methods.
TL;DR: In this article, a polyurethane foam medium was manufactured and characterized to determine its suitability as a solid support medium for use in gas-phase bio-filters.
Abstract: Although biological treatment has been applied successfully to treat waste gases using conventional organic packing media such as compost, there is currently a need for further research on ways to optimize the medium selected. Use of a superior filter-bed medium could overcome or minimize many of the problems encountered in conventional biofilter operation (e.g., medium clogging, difficulty in control of moisture content, and nutrient limitation). In research described herein, polyurethane foam was manufactured and characterized to determine its suitability as a solid support medium for use in gas-phase biofilters. Part I of this paper describes studies conducted to determine the medium's porosity, pore size, head loss characteristics, density, sorption capacity, and chemical resistance. Results are presented that characterize the polyurethane foam medium's properties and suggest how it can be used effectively in treating gas-phase volatile organic compound contaminants. Part II of this paper describes st...
TL;DR: An efficient approach for obtaining wasteload allocation solutions that provide the optimal trade-off between treatment cost and reliability and is nearly as accurate as the approach that links the GA with Monte Carlo simulation and is far more efficient.
Abstract: This paper presents an efficient approach for obtaining wasteload allocation solutions that provide the optimal trade-off between treatment cost and reliability. This approach links a genetic algorithm (GA) with the first-order reliability method (FORM) for estimating the probability of system failure under a given wasteload allocation. The GA-FORM optimization approach is demonstrated for the case study of managing water quality in the Willamette River in Oregon. The objective function minimizes the sum of the treatment cost and the penalty associated with breaching a reliability target for meeting a water quality standard. The random variables used to generate the reliability estimates include streamflow, temperature, and reaeration coefficient values. The results obtained indicate that the GA-FORM approach is nearly as accurate as the approach that links the GA with Monte Carlo simulation and is far more efficient. The trade-off between total treatment cost and reliability becomes more pronounced at higher water quality standards and is most sensitive to the uncertainty in the reaeration coefficient. The sensitivity to the reaeration coefficient also increases at increased reliability levels.
TL;DR: In this article, coal fly ash is used as a heterogeneous catalyst in peroxidative decolorization of aqueous solution of several reactive drimarene dyes using hydrogen peroxide (H2O2).
Abstract: This paper deals with the potential of coal fly ash as a heterogeneous catalyst in peroxidative decolorization of aqueous solution of several reactive drimarene dyes using hydrogen peroxide (H2O2)....
TL;DR: In this article, the authors evaluated feasibility of using an electrokinetic technique to remove hydrophobic organic pollutants from soils, with the assistance of a cosolvent ( n-butylamine, tetrahydrofuran, or acetone) added to the conducting fluid.
Abstract: This research was carried out to evaluate feasibility of using an electrokinetic technique to remove hydrophobic organic pollutants from soils, with the assistance of a cosolvent ( n-butylamine, tetrahydrofuran, or acetone) added to the conducting fluid. The experiments were carried out on glacial till clay with phenanthrene as the test compound. Desorption equilibrium was investigated by batch tests. The electrokinetic experiments were conducted using a 19.1 cm long 3 6.2 cm inside diameter column under controlled voltage. Water or 20% (volume) cosolvent solution was constantly supplied at the anode. The concentration of phenanthrene in the effluent collected at the cathode was monitored. Each experiment lasted for 100 to 145 days. Results showed that the presence of n-butylamine significantly enhanced the desorption and electrokinetic transport of phenan- threne; about 43% of the phenanthrene was removed after 127 days or 9 pore volumes. The effect of acetone was not as significant as butylamine. The effluent flow in the tetrahydrofuran experiments was minimal, and phenanthrene was not detected in the effluent. The use of water as the conducting solution did not cause observable phenanthrene migration.
TL;DR: In this article, the authors evaluated the effect of phosphate inhibitors on the corrosion of iron pipes under extended stagnant water conditions, and found that polyphosphate inhibitor dosing did not decrease the extent of scale buildup or overall weight loss.
Abstract: This four-year study evaluated the effect of phosphate inhibitors on the corrosion of iron pipes under extended stagnant water conditions. Study parameters included pH and alkalinity, age of the pipe, water stagnation time, and inhibitor type. For iron release, addition of phosphate inhibitors had no statistically significant effect (at 95% confidence) in two-thirds of the experiments. In the remaining experiments, addition of orthophosphate or zinc orthophosphate always increased iron concentration. Polyphosphate addition decreased iron release at only one water quality and increased it at other conditions. For weight loss, polyphosphate inhibitor dosing did not decrease the extent of scale buildup or overall weight loss. Orthophosphate dosing reduced overall weight loss at only one water quality condition; at all other conditions, the addition of orthophosphate had a detrimental effect.
TL;DR: In this paper, a polyurethane foam medium with characteristics described in Part I of this paper was tested in a toluene degrading biofilter to demonstrate its ability to support an active biofilm and to study feasibility of a novel nutrient addition and biomass wasting strategy.
Abstract: A polyurethane foam medium with characteristics described in Part I of this paper was tested in a toluene degrading biofilter to demonstrate its ability to support an active biofilm and to study feasibility of a novel nutrient addition and biomass wasting strategy A laboratory-scale biofilter was fed a model waste stream containing toluene for more than 300 days using empty bed residence times ranging from 1 to 4 min and toluene concentrations ranging from 50 to 200 parts per million by volume Results reported herein demonstrate that a polyurethane foam medium with high porosity, suitable pore size, low density, and an ability to sorb water was able to remove over 99% of the influent toluene after implementation of a nutrient addition and biomass removal strategy The strategy, made possible by use of the foam medium, overcame problems such as clogging, high head loss, moisture content control, and nutrient limitation that are often associated with conventional biofilter operation
TL;DR: In this article, a non-point-source planning model was modified to simulate long-term nitrogen (N) and phosphorus (P) transport from rural watersheds, and the model was validated on two small watersheds without calibration and on a large watershed with calibration of only the sediment detachment parameters.
Abstract: ANSWERS-2000, a non-point-source planning model, was modified to simulate long-term nitrogen (N) and phosphorus (P) transport from rural watersheds. The model simulates infiltration, evapotranspiration, percolation, and runoff and losses of nitrate, adsorbed and dissolved ammonium, adsorbed total Kjeldahl N, and adsorbed and dissolved P losses. Eight soil nutrient pools are modeled: stable and active organic N, nitrate, ammonium, and stable and active mineral, organic, and exchangeable P. The model was validated on two small watersheds without calibration and on a large watershed with calibration of only the sediment detachment parameters. Predicted cumulative runoff, sediment, nitrate, dissolved ammonium, adsorbed total Kjeldahl N, and orthophosphorus P losses were within a factor of 2 of observed values (-40 to +44% of observed values). Predictions of individual runoff event losses were not as accurate (-98 to +250%). The model seriously underpredicted adsorbed ammonium losses by up to 97%, and additional work is recommended on this submodel. In a practical application, the use of the model in evaluating the cost-effectiveness of alternative management scenarios was demonstrated.
TL;DR: Analytical solutions of the homogeneous surface diffusion model with no external mass transfer limitation are used to evaluate adsorbate concentrations in the solid phase as a function of time.
Abstract: Adsorption is modeled when powdered activated carbon (PAC) is applied in continuous-flow reactors followed by membrane filtration units operated without carbon wastage between backwash events. Four reactor configurations are studied: (1) a membrane reactor dosed with a step input of PAC; (2) a continuous-flow stirred tank reactor dosed with a step input of PAC and followed by a membrane reactor; (3) a plug-flow reactor dosed with a step input of PAC and followed by a membrane reactor; and (4) a membrane reactor dosed with a pulse input of PAC at the beginning of the filtration cycle. A steady-state operation is considered to describe the adsorption process through the continuous-flow stirred tank reactor and plug-flow reactor, whereas adsorption in the membrane reactor is modeled as a non-steady-state process. Adsorption kinetics is assumed to occur by homogeneous surface diffusions, and adsorption equilibrium is described with the Freundlich isotherm model. Analytical solutions of the homogeneous surface diffusion model with no external mass transfer limitation are used to evaluate adsorbate concentrations in the solid phase as a function of time. Part II of this study presents model simulations and verification with experimental data obtained in a bench-scale apparatus.
TL;DR: It is hypothesized that mobile bed streams are susceptible to blooms during summer low flows following floods because (1) they usually lack temperature tolerant snail grazers; and (2) mayfly recovery lags behind algal regrowth, and there is a short period when algae escape from ''top-down'' grazer control.
Abstract: A computer model for epilithic algae and grazer biomass in streams is modified to better predict the effects of temperature and is calibrated for diatoms and mayflies. Mayflies are predicted to maintain low diatom biomass provided that (1) temperatures remain within their preferred range (10-207C); and (2) mayfly populations are not adversely affected by floods. Algal blooms are predicted to occur in mayfly-dominated streams above 207C—temperatures common in pasture streams over summer. We hypothesize that mobile bed streams are susceptible to blooms during summer low flows following floods because (1) they usually lack temperature tolerant snail grazers; and (2) mayfly recovery lags behind algal regrowth, and there is a short period when algae escape from ''top-down'' grazer control. Proliferations of periphytic algae (algal blooms) have been documented in a number of New Zealand rivers with stoney beds draining agricultural catchments (Biggs and Price 1987) and adversely affect ecosystem structure and function, river aesthetics, and some water uses. Most conspicuous are blooms of filamentous green algae, although proliferation of diatoms and blue-green algae are also of management concern. Algal blooms only occur sporadically, when the rates of accrual (au- totrophic fixation plus colonization) exceed the rates of loss (sloughing, flow disturbance, and consumption by grazers). Benthic macroinvertebrate grazers (principally aquatic in- sects) have a significant negative effect on algal biomass; for example, Welch et al. (1992) showed that 3,000 grazers m 22